Transmission loops providing a data bus connecting several peripheral units are well known in the art.
Any suitable data format may be used within such transmission system, one example being Manchester coding. Regardless of the data format chosen, the data structure must be accurately repeated so that the proper synchronization and interpretation of the data can be accomplished by the peripherals in the loop.
In transmission systems, and especially loop transmission systems as shown in the above patent, data of a particular length is placed within a transmission system and this data is recirculated. In many cases, a data stream is placed in the transmission system. As the data stream consists of data pulses traveling within the transmission system at a known propagation rate, the system length will occupy a finite distance or physical length and its length also may be defined by the time for that data stream to pass a single point in the transmission system. In many cases, this length is longer than the electrical length of the transmission system and a portion of the data must be accommodated outside of a physical transmission line.
Additionally, as peripherals are added or taken from the line the transmission system will contract or expand. Contraction or expansion may also result from changes in temperature and from other effects which change the phase of the data signal at a data line output or input port.